(a) Field of the Invention
The present invention generally relates to an inverter control apparatus. More particularly, the present invention relates to an inverter control apparatus that offers a soft turn-off to a gate operation of an inverter to securely protect an IGBT.
(b) Description of the Related Art
FIG. 1 shows generally a portion of a power system of an electric vehicle.
As shown in FIG. 1, the power system includes a gate operating portion 10, an inverter 20, and a motor (M).
The gate operating portion 10 outputs a PMW signal to an inverter 20, depending on a driving demand, to control speed/torque of the motor (M). As shown, the inverter 20 has a plurality of IGBT(Insulated Gate Bipolar Transistor). The inverter 20 transforms high voltage DC power supplied from a DC link (Vdc) by switching the IGBT per each phase to 3 phase AC power according to a PWM signal transferred from the gate operating portion 10. The 3 phase AC power is supplied to each phase of the motor (M). The motor (M) is, thus, driven by the 3 phase power supplied from the inverter 20 through a power cable to output a rotation speed/torque,
While FIG. 1 illustrates an electric vehicle in particular, the inverter and the motor can also be applied to an electric vehicle, a hybrid vehicle, and a fuel cell vehicle.
In a vehicle in which the inverter and the motor are provided, the inverter 3 phase power can generate a short circuit as a result of a collision, poor maintenance, deterioration of a power cable, and an error made in the assembly process.
If a short circuit is generated in the inverter 3 phase output, over current forms in the IGBT, and the gate operating portion 10 detects over current so as to prevent a damage of the IGBT by the over current and forcibly stops switching (forcible turn-off).
However, if over current is formed in the IGBT, a sharp switching off induces excessive voltage (voltage over shoot) at both ends of the IGBT. If the excessive voltage is larger than a predetermined voltage for the IGBT, the IGBT can be damaged.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.